The present invention relates to a cathode ray tube, particularly to a cathode ray tube wherein an optimum flute portion is formed utilizing a computer simulation.
A cathode ray tube is an electron tube wherein a picture is displayed on a screen through a method wherein electron beams emitted from an electron gun are deflected by horizontal and vertical magnetic fields of a deflection yoke. The deflection yoke is installed on the outside surface of a funnel of the cathode ray tube. The electron beams reach the fluorescent body of the screen as vertically and horizontally deflected beams.
In a conventional cathode ray tube, a cone portion of the funnel, whereon the deflection yoke is installed, has a circular cross-sectional shape. Further, a panel section that forms the screen and the region adjacent to the panel has a rectangular form.
However, the above cathode ray tube has a drawback in that a superior picture display is hard to achieve due to the beam shadow neck (BSN) phenomenon in which electron beams deflected by the deflection yoke and intended to reach the corner portions of the screen hit on an inside wall of the cone portion of the funnel.
Because the BSN phenomenon occurs principally in the cone portion of the funnel that is located opposite to a diagonal portion of the panel, grooves to prevent the BSN phenomenon are formed around the diagonal portion on which electron beams are hitting. The groove formed around the diagonal portions of the funnel is called a flute portion.
Recently, the above mentioned cathode ray tube has faced requirements that power consumption be spared for the sake of energy conservation and power efficiency, and that the release of magnetic fields should be strictly regulated to minimize the influence of electromagnetic waves on computer users for the sake of their health. Therefore, at issue now is how to lower power consumption of the deflection yoke which is the location of highest power loss.
For enhancement of product integrity and product quality, improvement of screen brightness and fine resolution picture should be achieved first. Electric power for the deflection yoke should be increased to achieve this purpose.
To improve screen brightness, the anode voltage charge for finally accelerating electron beams should be increased. As a result, increased electric power for deflection is needed to deflect the accelerated electron beams. Increased power for deflection is also needed when deflection frequency is increased to achieve a high resolution picture.
When wide angle deflection (e.g., 100xc2x0, 110xc2x0)is required for a thin television receiver because of the shorter length of the cathode ray tube, it can be realized by an increase of deflection power or an improvement of deflection sensitivity.
However, increased power for deflection leads to an increase in the strength of a generated magnetic field and an increase in power consumption. Therefore, a technique of enhancing deflection sensitivity and deflection efficiency is needed wherein increased brightness and a superior resolution picture are achieved and wide angle deflection performance is made possible while providing the same amount of power or less for deflection.
Accordingly, a technique for a cathode ray tube is provided wherein an outside circumferential shape of the funnel cone portion equipped with the deflection yoke is designed such that deflection of the electron beams becomes increasingly greater as they travel from a neck to a panel and can make various trajectories such as a circular or rectangular pattern. Accordingly, deflection sensitivity and deflection efficiency are enhanced by a minimized size of the cone portion equipped with the deflection yoke and by an installation of the deflection yoke closer to electron beams.
In the cathode ray tube of conventional structure wherein an outside circumferential shape of the cone portion is made in an ellipse or rectangular form, frequent BSN phenomena occur and deflection sensitivity decreases when the thickness of diagonal portions increases. However, thin diagonal portions can cause collapse of the funnel due to insufficient strength of the funnel against the inner pressure.
A cathode ray tube according to the present invention is provided to solve the above problems. A cathode ray tube is provided wherein BSN phenomenon can be prevented and enough structural strength against inner pressure is provided, because the cathode ray tube has an optimum flute portion designed with the help of a computer simulation wherethrough electron beams orbits and funnel stress are interpreted.
A cathode ray tube according to the present invention comprises a panel that forms a screen on an inside face thereof, a funnel connected to the panel and having the deflection yoke on some outside circumference thereof, and a neck connected to the funnel. Inside the neck, an electron gun is installed by insertion thereinto.
A flute portion is designed such that a cone shaped outside contour of the funnel equipped with the deflection yoke changes from a circular shape to a non-circular shape as it travels from the neck thereof to the panel thereof. The cone portion of the funnel has grooves that are formed inside the edge portion of a diagonal line along a longitudinal axis direction of the cathode ray tube.
The flute portion is also designed such that a line indicating a changed flute angle along the cone portion of the funnel has at least one maximum angle between the neck seal face and the standard deflection position when a flute angle is defined as an angle formed between the diagonal axis line and a line formed on a vertical plane by connecting an edge point of the flute groove and the origin that is on the longitudinal axis line of the tube.
The flute portion is further designed such that the changed flute angle along the cone portion of the funnel flatly decreases from the standard deflection position to the inflection point.